Ancient Microorganisms and Carotenoids Preserved in Fluid Inclusions in Halite from Chaka Salt Lake, Western China: Evidence from Micro‐observation and in situ Raman Spectroscopy

Abstract

Trapped ancient microorganisms in halite fluid inclusions are of special interest to the understanding of biology and ecology in salt lake systems. With the integration of petrologic, microthermometric, and Raman spectroscopic analyses, this study utilizes fluid inclusions from Chaka Salt Lake, eastern Qaidam Basin, NW China, to assess the possibility of microorganism‐trapping by fluid inclusions. Here, we report that the solid phase of some primary fluid inclusions contains carotenoids, which is interpreted as evidence of Dunaliella algae, and that the coexisting liquid phase comprises SO42‐. The homogenization temperatures of single‐phase primary fluid inclusions indicate that the precipitation temperature of the Holocene halite in Chaka Salt Lake ranges from 13.5°C to 36.4°C. This suggests that fluid inclusions in halite are a good medium for trapping and preserving ancient microorganisms and organic matter in salt lakes, and that Raman spectroscopy has good potential to identify halophilic archaea.

Geochemical and Biological Profiles of a Quartz Stone in the Qaidam Mars Analog Using LIBS: Implications for the Search for Biosignatures on Mars

“…Previously, only possible derivatives, dimethyl diaryl isoprenoids, of β-carotene were discovered in a saline lacustrine setting in western Qaidam, 78 and algal carotenoids were detected in halite from an eastern Qaidam hypersaline lake. 79 In this study, we find that β-carotene universally occurs at the bottom of the sampled clastic quartz stone, as well as some lower parts of its side, indicative of the presence of biotic signals. However, the signal of β-carotene is absent on most of the upper parts of the rock (Figure 4), indicating a comparatively infertile niche under the harsh subaerial conditions.…”

“…Despite previous detections of carotenoids in the Atacama Desert and Mojave Desert, , to our knowledge, it is the first time that the carotenoid, typically β-carotene, was found in the hyperarid western Qaidam Basin by Raman spectroscopy (Figure ). Previously, only possible derivatives, dimethyl diaryl isoprenoids, of β-carotene were discovered in a saline lacustrine setting in western Qaidam, and algal carotenoids were detected in halite from an eastern Qaidam hypersaline lake . In this study, we find that β-carotene universally occurs at the bottom of the sampled clastic quartz stone, as well as some lower parts of its side, indicative of the presence of biotic signals.…”

A first insight into the Polish Bochnia Salt Mine metagenome

“…The results indicate that halite-trapped archaeal communities were resilient to entrapment durations of up to 21 weeks and that such a halite entrapment may be an effective survival strategy for haloarchaea (Huby et al 2021 ). In addition, ancient microorganisms trapped in halite fluid inclusions were identified in the USA, China, and Australia (Chen et al 2021 ; Vreeland et al 2000 ). Moreover, 830-million-year-old cell forms in fluid inclusions were observed in halite from Browne Formation (Australia).…”